The invention relates to ophthalmic lenses useful for the correction of presbyopia.
As a person ages their eyes are less able to accommodate, or bend the natural lens, to focus on objects that are relatively near to the observer. This condition is known as presbyopia. Similarly, people who have had their natural lens removed and an intraocular lens inserted as a replacement do not generally have the ability to accommodate.
One method to correct for the eye's failure to accommodate is known as monovision in which a single vision lens for correction of distance vision is used in the dominant eye and a single vision lens for correction of near vision is used in the non-dominant eye. Monovision typically results in a loss of stereopsis. Another method for treating presbyopia is the use of bifocal or multifocal contact lenses in both of the individual's eyes. Satisfactory corrections can be obtained with this method but it typically results in a reduction of image contrast and resolution compared to monovision. Yet another method of treating presbyopia is modified monovision. This involves a bifocal or multifocal lens in the first eye and either a single vision lens or a bifocal or multifocal that is different than the first eye lens in the second eye. Modified monovision can require consideration of a large number of possible lenses in order to provide satisfactory lens performance.
Having a family of lenses across a complete or nearly complete range of lens power requirements that optimally correct near vision preferably with the concomitant correction of distance vision is still desirable.